The present invention relates to multi-unit railroad freight cars, and in particular to such a car including container well units.
Within the limits of available space along railroad tracks and the ability of the tracks to support loaded freight cars safely, it is economically desirable to carry as heavy a load of revenue-earning cargo as possible in a given train length. Increased cargo weight for a given train length gives increased cost efficiency, since the train crew wages, train mile and fuel expenses, and locomotive costs are shared by the increased amount of cargo revenue.
Freight cars including multiple well units for carrying stacked intermodal cargo containers are well known. Some of these cars have shared trucks to support adjacent well units. Others use drawbars to interconnect adjacent units that are each fully supported by their own trucks. In both of these types of multi-unit container well cars the large space between the ends of containers carried in adjacent well units results in a significant amount of aerodynamic drag during train operation and leaves a significant portion of the length of a train in which no cargo containers are present.
Within the railroad industry there are regulations in effect limiting the maximum weight of a loaded intermodal cargo container, and railroad cars are designed with ample strength to carry various combinations of capacity of such cargo containers safely and not exceed the capacity of the freight car. For example, containers of nominal 20-foot length are limited to 52,900 pounds, nominal 40-foot containers are limited to 67,200 pounds and nominal 53-foot containers may be designed for either 56,700 pounds or 67,200 pounds.
These maximum weights must be considered when loading a railroad car in order not to overstress the car body or overload its trucks and thus concentrate too much weight on the tracks. As a result, a well unit carrying two fully loaded 20-foot containers may not be able to safely carry a fully loaded 40-foot or longer container in an upper tier.
Utilization of shared trucks between adjacent well units for carrying stacked containers in such multi-unit railroad freight cars also requires restricting the weight or number of containers which can be carried stacked in those adjacent well units carried by a single shared truck, in order to avoid overloading the shared truck. This often results in the unshared truck at each end of such a multi-unit car being significantly under-loaded. As a result, such multi-unit well cars with shared trucks are often loaded to less than the optimum ratio of load weight to the length of a train of such cars.
What is desired, then, is a container-carrying, multi-unit railroad freight car that can be loaded to utilize more fully the available carrying capacity of the trucks with which such a multi-unit car is equipped, and in which the cargo weight for such a car of a given length and container well size is maximized.
The present invention overcomes some of the aforementioned drawbacks and provides an answer to some of the shortcomings of the prior art railroad cars mentioned above by providing a multi-unit railroad freight car for carrying containers, in which at least two container well units each include a container well and have respective body bolster structures adjacent their ends, in which a plurality of shared trucks each support an end of a respective one of the container well unit body bolster structures, an intermediate unit is located between two of the container well units and has a pair of opposite ends each supported on a respective one of the shared trucks supporting an end of an adjacent container well unit, and in which a container support structure included in the intermediate unit extends above the body bolster structure of the end of the adjacent container well unit.
In one embodiment of the invention the multi-unit freight, car has an intermediate unit that includes an elongate center sill including opposite sill ends and has an articulating coupler associated with each of the opposite sill ends.
One aspect of the invention is the provision of a multi-unit railroad freight car including an intermediate unit that includes a pair of transverse bolsters each attached to a center sill, and in which at least one of the transverse bolsters includes a side bearing support arm aligned with a corresponding side bearing foundation located on a respective shared truck.
In one embodiment of the invention an intermediate unit for a multi-unit railroad freight car includes a pair of container support arms associated with each of the opposite ends of the intermediate unit, and a portion of each container support arm is located above an end structure such as a body bolster of the adjacent container well unit of a multi-unit car including such an intermediate unit.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.